Preheat the oven to 350°F (180°C). Lightly grease a 24-cup mini muffin pan with cooking spray or a little vegetable oil.
Unroll the pie crust onto a work surface. Using a round cutter about 2 inches (5 cm) wide, cut out 24 circles. If needed, gather the scraps, roll them out again, and continue cutting until you have enough.
Press one pastry circle gently into each muffin cup, covering the bottom and sides. Prick the base of each shell a few times with a fork.
Bake the pastry shells for about 10 minutes, until they just begin to turn lightly golden.
Remove the pan from the oven. Spoon just under 1 teaspoon of cranberry jam into each shell, then place one piece of brie on top.
Return the pan to the oven and bake for another 5 minutes, until the brie is soft and slightly melted.
Let the bites rest in the pan for about 10 minutes.
Carefully remove them from the pan, using the tip of a knife around the edges if needed.
Sprinkle with chopped fresh chives, if using, and serve warm.